Compressor unloading apparatus



May l2, 1953 A. B. NEWTON 2,638,265

COMPRESSOR UNLOADING APPARATUS Filed Jan. 3, 1948 3 Sheets-Sheet l INVEN TOR. HZu/Qz ,3. New far?- owl ira/r/VEYS.

A. B. NEWTON COMPRESSOR UNLOADING APPARATUS May 12, 1953 Filed Jan s,1948 May 12, 1953 A. B. NEWTON 2,638,265

COMPRESSOR UNLOADING APPARATUS Filed Jan. 3, 1948 3 Sheets-Sheet 3iffaF/vI/S Patented May 12, 1953 COMPRESSOR LOADING APPARATUS Alwin `B.Newton,'-r.Dayton;:-ho, `to lChrysler Corporation; Highland Park, Mich.,a

corporation vof Delaware Vapplicmionuanrifary s, 194s,-ser1aiNu;-444

This invention Vrelates toirefrigerant-compressors and moreparticularly-to improved-f apparatus for selectively loading1and-unloading-cylinders thereof 'in response to-predeterminedopern. aan;

ating conditions.V y *Compressor unloading mechanisms and moreparticularly the unloading mechanism described in Patent No;*2,-185A7-3g1 which Yissuedata CNB/ Neesonv on January 2,--1f947,-are-dependent-upon mechanical Alinkages to operate a masterffcontrolcylinder.u VIt is`-anobject oft-this''inventicneto substitute ahydraulic means-tocontrolf'amaster cylinder. 'A more 4sensitivecontrole-lisg possible with the hydraulic unloadingl mechanism-LthanVwith the mechanism" described inlPaten-t y*No2- 2,185 ,47f3; IthasLbeen--observed thateaschange of--approximately 2- pounds of -suctionpressure is required'tob cause the apparatus of the patent to movesufficiently to-1oadneof thefcompressor cylinders. YIt is` desirablelto-have a'l-change of approximately 3 pounds in suctionpressure-producea lchange iromna'complete loading fitoa minimum loading'of thecompresscilrsoriviceversa. Therefore,V V*ai mechanism --requiredwhichiis sensitive venough 'to respond toa change-in- -suc- I tionpressure equal to a small increment `of-'th'e desired `threepoundwspread; The Size ofUthe increment is determined -byUt-he'number4ofec'yl'- inders' to be controlledrby-rtheeunloadinglmechaf Anism;Mk Itis an 'object-ofthisiinvention-to provide acontrol With-therequired-`sensitivity.f --Itis-afurther object' ofthe inventionut 'videa compressorbunloading mechanism in whichsmall'forces-and-reducedLmovments-of the 'coin-' ponentLpartsvaresufficientetoleload'A orl'unl'oad i position assumed by themastcrya-lveof f the unloader is the resultant. of apluralityofrcontrolling operating.iconditionsersting inthemot'or'compressor set. ,The composite controlapparatus is thus 'capablfrslving''a plurality-of conditions to dtermine :the-:optimum annt nofcompressor...f1oading.: The' hydraulicdmeansor 'controllingthe position'iofithe mas'trl'valve:.:the

unloading apparatus-is particularly-adapted -to be influenced byl amultiplicityiof control factors. 1A mechanical control of `the mastervalve as delscribed in Patent-No. 2,185,473 does not lend itself readilyto control in response to moretha'n one operating condition. L-

1t is an` additional object of the invention to provide va means :forinterrupting the-supply 4of oil .tounloader pistons associated with thecompressor cylinders Vwhere that means so operates that thcolsupply'linetolan individual cylinder is eitherropenorclosed-.and is.never partially closed-.With a throttled oil-supply passingtherethrough. .l ,1 i i2 rf. ,j .Y .15

It? is a efurthervobject' ofthe linventionfto asso# ciate :with ahydraulically operated master control valve a means to dump thecontrolling-.oil :from the valvevvhen predetermined suctionpressures-are exceededby. the compressor. This provides asafety devicewhich prevents overloadingof the compressorfN/f i .L It 'isi anadditional'object of the invention to provide means .tovary theipressureof .oilldelivered to 'Ta hydraulically'op'eratedmaster 'control valveinwrespo'nse 'Ltol overheatingk of -the motor vdriving thecompressorand'in. response to Athe presence .of yanexce'ssive amount'of electric.current in the iield coil ofthe motor.H .y 1 f It is a furtherfobject'of the invention to pro- -vid'evmeansktoautomatically load onecompressorcylinder at thesearliestpossible. moment after .starting the compressor.This is vaccomplished lby concentrating theA entire output of the com-'-presser oil pumpen oneunloader piston yuntil-the voil pressure'isvvsufficiently high'v to "indicate that enough oil is being supplied tooperate: through the'rnormal unloader system involving all of thecompressor unloadercylinders. The presence of refrigerant in theoiljvvvhich occurs'after approlonged shutdown makes thisfyeature oftheunloader'` mechanism particularly desirablebecau's'e a 4mixture ofrefrigerant''suchv as Freon and'oil cannot be pumped to as high apressure as could oil'itself.` Thus, if evenlfone` cylinder canfbeloaded immediately after starting, the refrigerant `can-be -pumpedout-ofthe oil-and normal operation of 'fthe compressor can rheobtained-more quickly: y@

Other objects and advantages vvill become more apparent from thefollowing description takenin connection, with theaccompanyingdrawings-in Fig. 1a. side..e1evaton of.- a.refr igera.nt;,QQ.Inpressorcoupled-...tma motor;. f

Fig. 2 is a vertical section taken through the compressor of Fig. l;

Fig. 3 is a View partly in section and partly diagrammatic showing aportion of the compressor and the unloader controls associatedtherewith;

Fig. 4 is a View partly 'in section and partly diagrammatic "showing amodified fform 'of `control responsive to thear'nount ofcurrent owing inthe motor of the motor compressor set;

Fig. 5 is a view taken on the line 5-5 of Fig. 3;

and

Fig. 6 is an enlarged View of la portion 'f FigQB.

In Fig. l a motor compressorset'incorporating my invention isillustrated. Acmpresscr lil is supported by a base l2 and adapted to bedriven by an electric motor i4. The armature it of motor I4 is coupledto the main shaft i3 ofthe compressor. The compressor is illustrated inmore detail in Fig. 2. 'Ilie compressor illustrated inFig.2'comprisesfahousing V2l) provided with a bearing 22 inWhichthe-shat lil-'is journaled. A conventional seal -24 may be employedbetween theshaft I8 and housing 2i) in order to prevent theescape ofrefrigerant from the compressor housing.

t The shaftA |18 includes'a pair of counterbalances 26 and 28 whicharelocated thereon .and which tend to smooth vibration byacting'as'lywheels. The front end of the shaft beyond the bearing 22 isprovided witha crank pin 30 which is lsurrounded by a bearing ring 32forming the bearing surface for a plurality of piston rods 34. Thenumber of piston rods corresponds to the num? er of cylinders-inthecompres'sor. The Weight of the'crank pin is counterbalanced by abalance weight 36.

-Each piston rod-34 extends radially towards its associated cylinder 38.The cylinders are-radially, equallyV spaced about the center lines ofthe compressor. Each cylinder is ofiset-longitudinally of the compressorby anlamount equal tothe distance between centers ofthe piston rods Sli.Eachcylinder'comprises a linerdil which is inserted throughv the outerend ofthe cylinder when aA cylinder head 42 isV removed. A suctionmanifold 44 surrounds the liners vand communicates With a refrigeratingsystem (notshown) through a suction port provided inthe housing" and`not illustrated herein. rThe suction manifold 44 com- L municates withthev interiord `of the compressor housing through a'plurality ofopenings t8. The suction manifold is also in communication with thelinterior of the vrear or right `hand portion of the compressor of Figt2 through oneV or more A openingsn50. The entire interior oi thecornpressor is therefore subjected to pressure equal to the suctionpressure of the refrigerating system 'with Vwhich it' is associated.

The 'refrigerant "entering the compressor through the 'suction/manifold'44` is' admitted to each cylinder space through suction valves "v 52.'The' gas'is="admitted' upon raising 0f' the"4 suction valve 52 anddischarged v'from 'the cylinder' upon the-'raising of a dischargevalve-54. Piston 5t is adaptedtoreciprocate in-li-ner'-'li0. The detailsad operation of t-he piston," seal, liner andvalve assemblyaremorefullyset-iorth in Neeson Patent No. 2,137,965, dated November 22,4938.'-Eachof the discharge'ports 58 extends through 'thei'iain housingv20:*si-iid-`pa'ssesi from the com- Jp'ressorthrough ai' frhainldischarge portl As described in Neeson Patent No. 2,185,473 a'meansvi'or producing dill-pressure is-provided' at Oil pressureproduced iss-used to'iubricate 4 moving `parts of the compressor and tooperate an unloader mechanism to be described. A master valve (it isassociated with the unloader mechanism and is adapted to control thedelivery of oil pressure to unloader mechanisms associated with eachcompressor cylinder. Oil is delivered under pressure from means E32 tomaster valve 313. A plurality of tubes (i5 connect the master lvalve iii`to individual unloader 'mechanisms associated with each compressorcylinder. One such unloader mechanism is illustrated in Figs. 2, 3 and 5and comprises a passage 68, a bore 'it and a member ll which has aportion sealed in bore it .rand-nasa ring portion 'i2 which surroundsliner 40. vRingportion `12 is provided with a channel 573 and-ringpiston i4 is adapted to reciprocate in channel i3. A port l5 connectschannel with bore "l0 so that'iluid admitted to bore l@ may enterchannel i3 and raise piston ld. A plurality of circumferentially spacedunloader pins 32 longitudinally-einher it .and are adapted to liitsuction valve 52 so that the suction valve is held in its open positionwhen piston llt is not raised by `iluid pressure. In such case gasentering the cylinder space through the suction valve forced back intosuction manifold M. Since the discharge valve remains seated the neteffect is an accomplishment of no usual Work. A ever 'it associated witheach unloaderpin t2. Each 'it is `pivotally mounted at l'! and has oneend thereof secured to a pin v82. The other oi' leach lever l@ isprovided with a depending pcrtion lwhich is adaptedto engage the pistonM A spring 'i9 is providedrto retain portion lil in contact with piston'Ht and 'to raise pin 225i when fluid pressure is not `present belowpiston lll. Pins 82 are adapted to open suction valve and "unload thecylinder when iluid pressure is not present below the piston lli.

When the system is at rest, the suction valves are held in `openposition due to the lack of oil pressure beneath the piston lll. Whenthe motor is starting the reciprccation of the compressor pistons 56will result in no `compression being p formed. However, as the motorreaches a higher speed and oil pressure is built up sufficient pressurewill be available-to load the compressor cyl-- inders by movement ofpistons lll.

Control mechanisms are adapted to control the delivery of oil to thepistons lli in response to predetermined motor and compressoroperatingconditions. The master valve @d comprises a housing 84 havingan axial bore t therein. A liner lB8 Whichalso contains an axial bore(it is secured withinrbore te and adapted to receive a piston 92therein. A spring 94 is contained withinthe boreil and acts upon one endof piston 92to urge it to the left in Fig. 3. The other end ofthe springt4 reacts upon a cap 96 secured to liner 88. A line @8 is adapted todeliveriiuid to or receive iiuid from a port itil in that-end of liner8S which is opposite to the 4endcarrying -the spring Siri. Therelationship between ythe strength of spring Elli and the pressure offluid delivered by line 98 will determine thevpositionof piston 92 inbore td. The central yportion of piston 92 is provided with a restrictedvdiameter so that a space lcd is provided between the portion 95 and thewall of bore 9U. Housing 184 and liner 88 are lprovided with cooperatingaligned openings "which form a port 106. A line |08 connects portyIBSA-with a source of yfluid under pressure. The housing 8a andliner-88l are provided with al plurality of aligned openings whichcooperate to. provide aA number .Qfl, axially` .spaceddscharse portsH01.-` Each dis- ;.charge port has aline r66 connected there- "to sothat fluid discharged from a port ||0 will .betransported to a passageand a bore 'l0 :associated with the unloader mechanism of one .of thecompressor cylinders. Fluid flow commu- ,nication Vis provided in mastercylinder64 from linelthrough inlet portl0li, space |04 to 1,dischargeports H0 when piston 92 is positioned .to accomplish this. Axialmovement of piston 92 in bore 99 can effectively block, oneor-more ofAthe discharge ports ||0 fromthe fluid delivered by line- |08. When any`discharge portl |0. is vso blocked oil is not delivered.. to :therelated bore ..10 and the compressor cylinder associated vwith lthatparticular port ||0lbecomes unloadeddue to the action of the spring 79in. its unloader lmechanism, The lines 98 and |08 .are preferably joinedto a common line ||2 Whichis connected Yto afsource of iluid underpressure.

i: Piston y92 `is preferably so. constructed thatno partial throttlingof the oil supply to anyone -Of'theilines AEivcan occur. The piston 92ypreferablycomprises an assembly of a first piston-ele- `ment 93 havingan axial rod-95 secured thereto :and a second piston element 91 slidablymounted on the rod 95. The piston elements l93- and 91 -areurged apart`by asmall 'spring 99 which is -weaker than spring v94..Thepiston--element 9'! :is provided with a plurality of circumferentialgrooves -|0|1- adapted L-tocoope'rate with a spring .loaded ball detent-|03 mounted in liner 88 to `rpositively positionpistonelement 91 at aplurality'of stations whichwill fully load or unload individualcompressorcylinders. AAzstopl |05 may .be provided to assure' ltheloading-of at least a 4minimum number of cylinders. f

To control the position of piston 92 in master valve 64 I have provideda control means I I4 which is associated with line 98. The controlmeans-H4 is-ad'apted to bleed fluid'from line -98hunder predeterminedconditions.r f Control means ||4 comprises a normally closed bleed Ailovalve- ||6 and cooperating valve Vseat |20 which 98. bellows ||8contained within Ycontrol means H4 is adaptedV to position valve H6,Valve modulates or entirely restricts-the owfof yfluid from controlmeans ||4 to line 98.v A spring v|22furgesbellows H8v against a stopmember |24 'whichcorresponds to a position wherein valve T|16s--positioned on seat '|20 and the flow 'of filuidinto control means H4is completely inter- 'rupted'hese components ofA the control means H4are'mounted'upona plate "|26 whichis at- -ta'chedto the compressorhousing 'I0 vby bolts 'i1-|28'. f A port |30 connects the interiorofbel- `lows ||8jwith the atmosphere. If'desired a f1tting |29 "may beprovided'to connect the interior of--bellows H8 to anl external controlmeans 'simnario that shownin my Patent-No. 2,581,329. 'A'cover |32 forthe control means I4 is provided -With'openings |34. As the suctionpressure withlinthefinterior'fl of the A'compressor housing falls thebellows A| 8 exten/ds" to open valve H6.4 'A lfiuidiiow communicationisV provided from valve "|`|6"t`o the compressor housingby tlfieopeningIin valveseat|20 and openin'gs'lS and |34. Oil thus'bled from line 9 8mayl fall by gravityto theisfumpn' the bottom 'o i the compressor housgand the Dressure.o`f ,`thelluid in lineiliim will beiseiermiilfdby Ithe' @eignet v0i reliefrrqvided bVv valviefflt.v Thefpositionof piston92isdeter- 891,93' 55.-. 9 ,-.-.lliis `position. wil1, ,1 etermir.1ewhch.0f the compressor cylinders are kia-dectA Continued operation..of the compressor with certain cylinders loaded will .reflectthischange in;suction pressure in the position of.piston 92. The newposition of piston 92 will load additional compressor cylinders therebyrepeating the cycle of increasing the suction pressure and repositioningthe piston 92.

vControl means |41oads cylinders as the suction pressure increases andunloads cylinders with y decrease in suction pressure.

.-A pairo orifices, and ||9 :are provided in vuidflow communication withline 98. An adjustable needle valve ||5 controls the discharge ofoilfrom line ||2 through orifice ||9 and therebyprovides means forvarying the sensitivity of the system. Orifice H'I'controls the rate ofchange of position of piston 92 for anyv given changein the opening ofvalve H6.

A manual controlma'y be associated with the controlmeans ||4 if rdesiredto provide a means for wedging the system toa loaded position. lIfhismanual control `includes anl adjusting screw |40 which is slidablylocked in a nut |42 carried by plate |26. A lock nut v`|44 is threaded.on screw |40. A spring |46 is `provided to extend, adjusting screw |40.A threaded cap |48maybe provided to cover this apparatus. Theoperatonbyremoving cap |40 and turning lock nut |44 `may retract screw |40 andpermityspring |23`tovseat valve l lli on seat |20 therebyrenderingcontrol H4 inoperative-and preventing its-interference ,withtheloading of `compressor cylinders. During periods of normal-.automaticoperation the lock nut |44 is removed so thatscrew |40 is not restrictedin its axial movement in response yto movement of bellowsy HB.

Supplemental controls may also ,be provided to unload compressorcylinders by bleedingoil from line 98 and bore 90 in .response to otheroperating-conditions of the compressor ormotor. The copendingapplication ofV C. R. Neeson, .Seri-al No. 786,273, led November 15,1947, which has matured into Patent No. 2,522,762, describes an improved-mechanism for bleeding. oil-froman .unloader apparatus in response toincreased suction pressure in a compressor thereby-permitting springsllSto unload compressor cylinders.y The hydraulic control meansV describedherein for master cylinder 64v is particularly adapted to operate inconjunction with they high suction pressure bleeding device described inthe Neeson application. This device is generally designated vby thenumeral |50 and is adapted to bleed iluid from bore in master valve 94.A port |49 is provided `in liner 88 and operatively connected `by a line|5I to control means |50. Port l|49 is preferably located axially inliner 88m such a position that piston element 93 will block this portuntil a predetermined minimum number of compressor cylindersV areloaded.r The control 1means |50 comprises a; housing |52ahaving acylinder |54. therein and abore |59 extending axially of the housing |52through one end thereof. A valve element |58 is adaptedto reciprocate inbore |56. Valve element |58 has an axial opening |60 extendingtherethrough andexposed -to the suction pressure existing in theinterior 54 :inthecompressorvhousing.. Legs |62, secure the valveelement |53, to the end portionpf` a collapsible. bellows, |64.,y Theother end ,othe belseaiedhy: mercenaire., casingl s2.

A spring |66 is provided within the bellows 1N and adapted to reactagainst an a-dusting screw |53 threaded through the top of the casing|52. Adjustment oi the screw |63 presele'cts the compression of Spring265. Spring'w'b resists collapsing of the bellows H54. Suction `pressuretransmitted from the interior '4B of the compressor through axialopening iiil to the cylinder |51l tends to compress bellows |84 therebyproducing linear movement of valve element 158 in accordance withvariations in suction pressure within the compressor. When the `suctionpressure is greatest the valve element |58 is moved inwardly in housing|52 and when the suction pressure is low spring |56 moves valve elementl outwardly. Valve element |58 is provided with a pair of adjacentrecessed portions v|`||l and Il@ in its surface. A spring pressed balldetent idt is adapted to enter recessed portion I'iil or recessedportion H2 depending on the position ci the valve element |58. A pin |16in housing |52 limits outward movement of valve element |58. 'Valveelement |56 is therefore provided with a first extended position asshown in 3 when the suction pressure is low and a second retractedposition when the suction pressure is high. i port its provided inhousing |52 adjacent the outer end of valve element |58 communicatesWith a chamber |80 and a passage Iii. The passage 82 is in fluid ilowcommunication with line |5| and port |519 which, as eX- piained above isin i'iuid iow communication With bore 9d and line @t unless port H59 isblocked by piston element 953. When valve element '|538 is in theposition shown in Fig. 3 the port |73 is blocked thereby and the fluidpressure in line e8 is unaffected by control 15|?. However, when thesuction pressure existing in the interior 't6 of the compressor becomesexcessive the bellows |54 is collapsed and the valve element |58retracted until ball Il'li drops into recessed portion VS2 therein. Thisprovides a fluid 'flow communication from line di* through passage |82,chamber li, port 1?'8 and bore it to the interior t6 of the compressor.This provides :a relief for oil pressure in line tu so that the numberof discharge ports l lis blocked by piston 92 is increased and morecylinders are unloaded. It is to be understood, however, that if desiredcontrol I5!) could be made responsible to discharge pressure or to bothdischarge pressure and suction pressure.

An additional control adapted to bleed uid from line @o and which isresponsive to operating conditions of motor ll may be provided. Thiscontrol has been designated by the numeral |90. The control tijdconsists of a temperature responsive valve |92 which is secured to thehousing of the motor The usual iield coil |94 of motor id isdiagrazninatcally illustrated and it is the temperature 'thereof whichWill determine the operation or' the valve H32. Valve |92 is connectedby a line it to line gli which is the source of fluid under pressure tomaster valve Bd. Line |95 Ableeds oilfrom line @t to valve ISE. A lineist returns oil from valve |92 to the interior it of the compressorhousing 2E). The valve |92 is provided with a hollow interior portionand a slidable element 2639. The slidaible element 29|) is adapted forlineaimovement within a guide 202. A port itil operatively connects theinterior of the valve |32 to the line m3. Slidable element 2G53 isadapted to selectively open and close port Zeil. The position ofslidable element 2|i0 is determined by the deformation or a bimetallicdis-k '296 located Within valve member |32 in close proximityto fieldcoil |94 of motor |13. A rod 129B opeiativelyconnects bimetallic element2136 and slidableeflement 290. When the temperature voi coil |84'becomes'excessive 'bimetallic element 20B denects 'to the right in Fig.3 thereby openjir'i'g port i204 `and permitting oil to be bled from line$8 tothe interior y#i6 of the compressor housing.

A 'resistance wire 20| may be placed in close proximity to thebi-metallic element 206, if desired. The resistance Wire 2M is connectedin series with the field coil |Sl of motor I4 and adapted'to Aheat theb'ivmetallic element 2% when :an excessive amount .of electric currentis present in the field coil |94. lThe resistance wire 20| possesses'anadvantage over the use of direct motor Aheat to actuate birnetallicelement 2&6 in that the response .is fquicher. 'In .the event of motoroverload an interval 'of .time is required for the entire motor'to heatup. Resistance 23| heats up much faster.

vA' modiied former control responsive to motor `overload'is illustratedin Fig. 4. A valve |92 which is simi-lar to the valve .illustrated inFig. 3 'is jprovidedwith arod 28 which comprises the move-ble portion4of a solenoid 2135 and operates Wit-hina sealed tube in solenoid 2t?)as is common solenoid valve construction. The solenoid` 285 visconnected series with the eld coil '|94 of mot-or I4 and is adapted tobe actuated to move element 260 to a lposition providing a iiuicl flowcommunication .between lines |96 and |98 when va predetermined excessiveamount of curn rent passes through 'field coil left of motor |55.

One or all 1 of these means for bleeding oil through line |96 in.response to motor overload may be used in an installation.

Operation In the operation `of-lt-he control device hei-ein described itwill be seen that fluid under pressure such as 4oil kis deliver-ed toline ||2 by lubricating pump Y62 and that ,line |12 ydivides, to formlines 98 and .|08 with the .line Hi8 serving as the source of iiu'idtobe selectively delivered to a plurality oi"` lines Blunder thecontrolof a master valve lill. Each of the'.l'inesv-it` is connected to a port|10 and the .ports 'HU are spaced axially along master valve 6l so thatthe position of piston 92 determines which ports IIU are incommunication with fluid supplied by line Hi8. Each of the lines' ABtlisadapted to deliver iiuid to the unloading "mechanism described hereinand associated with individual cylinders to vload these cylinders whenoil is delivered thereto. The position of the piston 92 in the mastervalve is determined by the fluid 'pressure supplied to the master valvethrough branch line 9.8 and the modulating valve 1M is adaptedto bleedoil from line 9i! thereby reducing the pressure on piston 92 as thesuction `pressure decreases. In other words, as the suction pressureincreases the modulating valve lil 'bleeds less fluid from line 98thereby increasing 'the oil'pressure on 'piston 92 and forcing piston 92to the right in Figs. 3 and 6 to expose additional ports II to oildelivered by line |68 to load more of the cylinders.

The' lcontrol device iii) is provided 'to bleed iiuid from 'mastervalve'd and permit spring 9i to move p`iston'92 to theleft to unloadadditional ycylinders when thevsuction pressure exceeds a predeterminedvalue and piston 92 vis located in a position corresponding to theloading of a predetermined number `of Acompressor cylinders so that'port|49 is uncovered; 'It will be noted that modulating valve I I4 bleedsthe greatest amount vice |50 operates to bleed' oil through orice |49lwhen the suction pressure is great enough to collapse bellows |64.

An additional control |90 is provided to bleed fluid from line 93 and.cause cylinders `to be unloaded When the operating conditions of /theimotor I4 indicate that this Would be desirable by opening theytemperature responsive valve |92.

The temperature responsive valvey |92 is opened when the motortemperature becomes excessive or when the amount of electric currentpresent in the eld coil |94 becomes excessive.

initial'loadingof onenor more compressor cylin-Y ders is hereinafterdescribed.

An additional supplementary control may be provided to assure theinitial loading oi one or more compressor cylinders and after a minimumpredetermined oil 'pressure is established to operate the unloadermechanism master valve 64. This concentrates the entire output'` of Vtheoil pump on the one or more unloader pistons until the oil pressure issuiiciently high to indicate that enough oil is beingv supplied tooperate through the normal unloader system involving all of thecylinders. This device is generally desig-V nated by the numeral 2I0 andis interposed in the uid supply line ||2 between the fuel pump 62 andthemaster valve 64. A line 2|2 connects the fuel pump 62 with the device24| 0. The device 2 I0 is provided with a housing 2 I4 having an inlet 2I 6 to which the line 2 I 2 is connected and having a first dischargeport 2|8 to which the line ||2 is connected and a second discharge port220 to which a line 222 is connected. The line 222 is connected vto oneof the lines 66 extending between the master valve 64 and the unloadermechanism of an individual cylinder. More than one line 222 could beprovided if desired and in that event each line 222 would be connectedto a different line 66. The line 66 is provided with a one-,Way valve224 which prevents oil delivered by line 222 from traveling to themaster valve 64 although it permits oil to travel from the master valvethrough line 66. The housing 2|4 of device 2|0 is provided With a port2|5 which connectsinlet port 2|6 and discharge port 220. A valve clement223 is adapted to selectively seal discharge port 2|8 and port 2|5 andcarries a valve'stem 230 Which is secured to a piston 232. The piston232r is adapted to reciprocate in a cylinder 234 provided in housing 2|4. A spring 236 urges piston` 232 to seat the valve 228 across dischargeopening 2|8. A port 238 provides a fluid flow communication betweeninlet port 2 I 6 and cylinder 234 above piston 232 so that the oilpressure existing in passage 226 exerts a force upon piston 232` tendingto unseat valve element 223 from opening 2| 8 and to seat it across port2|5.

limited time interval the oil pressure Will increase and the 'piston23,2 will be forced downwardly against l.springz23 thereby unseatingvalve elel An addieV tional supplementary control which assures theV Itywill thus be seen that when the compressor is initially started the pump262 Will deliver oilv through line 2I2, passage 226, line 222 lineY 66,

ment 228. This opens discharge port 2|8 and closes port 2|5 so thatsubsequently the oil delivered by pump 62 Will be transported by linesH2, |08 and 98 to the master valve 64 thereby permitting the operationof the compressor cylinders to be controlled by the mechanism previouslydescribed herein.

Althoug'hbut one specic embodiment of the invention is herein shown 'anddescribed it will be understood that various changes maybe made Withoutdeparting from the spirit of the invention.v` 1

1'. In ai motor 'driven multi-cylinder compressor-set having afirst-'means for unloading indivdual cylinders thereof, a fluid pressureresponsivev means adapted to selectively overrule the xedfmember and' arelatively Imovable member,

one of saidmembers being provided Witha plu` rality of"dischar'geportsand a first inlet port, said. movable meinberbeing adapted to controlthe communication of iluid from said inlet port to said individualdischarge ports in relation to its position relative'to said xedmember,'said`one member having a second inlet port for the admission offluid to position said movable member relative to said fixed inemben.means operatively; connecting said discharge ports with their respece'the ld'eliv'eryfof'fluid to said second inlet port inV response tosuctionfpressure in said compressor.

2. In "a motordriven` multi-cylinder compressorset', unloading meansfinconjunction With individual cylinders operable to unload thesecylindersvvhenthe,compressor is at rest, uid pressure creating meansoperating in unison with said compressor Aand creating suii'icientvpressure vat a minimum speedfto` overcome said unloading meansWherebykto load all of the cylinders, and unloadingy control meansresponsive to the pressure in: said compressor to connect or disconnectsaid fluid pressure creating means successively toorfrom nindividualcylinder unloading means, said control v'means rcomprising a mastervalve havingl a fluid owmconnection vvithfsaid fluid 'pressure' creating'means and adapted toY be positioned by iiuid pressure at'diierentpositions to connect or disconnect different cylinders with saidluid'pressure creating means and a suction pressure responsivejvalve ofthemodulating typeinterpose'd in said'fluid' flovv connection lto" controlthe ,posi` tion of' saidmaster valve by metering fluid to saidmastervralvrejin response to predetermined suction pressure`operatingvconditions o f said set.

In` a motor drivenrmulti-cylinder con'ipres` sor set having a rstmeansfor unloading individual cylinders thereofpa uid pressureresponsive meanswadapted to selectively overrule' the action of said rstmeans with respect to individual cylinders to load said individual cylinders under predetermined operating conditions, j means to deliver uidunder pressure to saidiiuid/ aeaaees pressure responsive means includinga source of fluid under pressure and a master valve adapted to bepositioned by said fluid, said valve comprising a fixed member and arelatively movable member, one of said members being provided with aplurality of discharge ports and a first inlet port, said movable memberbeing adapted to control the communication of fluid from said inlet portto said individual discharge ports in relation to its position relativeto said fixed member, said one member having a second inlet port for theadmission of fluid to position said movable member relative to saidfixed member, means operatively connecting said discharge ports withtheir respective iluid pressure responsive means, means to deliver iiudfrom said source to said iirst inlet port and means to deliver iluidfrom said source to said second inlet port, said last mentioned meansincluding a suction pressure responsive valve of the modulating typeadapted to bleed fluid from said master `valve and means forming a fluidflow connection between said master valve and said suction pressureresponsive valve including a port in said xed member positioned to beobstructed Vby said movable member until said movable member assumes aposition corresponding to the loading of a predetermined number ofcompressor cylinders.

4. In a motor driven multi-cylinder compressor set having a lirst meansfor unloading individual cylinders thereof, a fluid pressure responsivemeans adapted` to selectively overrule the action of said first meanswith respect to individual cylinders to load said individual cylindersunder predetermined operating conditions, means to deliver fluid underpressure to said fluid pressure responsive means including a source offluid under pressure and a master valve adapted to be positioned by saidiiuid, said valve comprising a iixed member and a relatively movablemember, one of said members being provided with a plurality of dischargeports and a first inlet port, said movable member being adapted tocontrol the communication of fluid from said inlet port to saidindividual discharge ports in relation to its position relative to saidfixed member, said one member having a second inlet port for theadmission of fluid to position said movable member relative to saidfixed membe i, means operatively connecting said discharge ports withtheir respective uid pressure responsive means, means to deliver iluidfrom said source to said first inlet port, means to deliver .fluid fromsaid source to said second inlet port, apparatus adapted to bleed fluidfrom said last mentioned means in response to predetermined operatingconditions of said set to thereby regulate vthe pressure of fluiddelivered to said second inlet port, and means to deliver all of thefluid from said source to the fluid pressure responsive means associatedwith at least one of the compressor cylinders and to by-pass said mastervalve until a predetermined fluid pressure is exceeded.

5. In a motor driven multi-cylinder compressor set having a iirst meansfor unloading individual cylinders thereof, a` fluid pressure responsivemeans adapted to selectively overrule the action of said rst means withrespect to individual cylinders to load said individual cylinders underpredetermined operatingl conditions, means to deliver fluid underpressure to said fluid pressure responsive means including a source offluid under pressure and a master valve adapted to be positioned by saidiiuid, said valve comprising a fixed member and a relatively movablemember, one of said members being provided With a plurality of dischargeports and a rst inlet port, said 'movable member being adapted tocontrol the communication of fluid from said inlet port to saidindividual discharge ports in relation to its position relative to saidlixed member, said one member having a second inlet port for theadmission of fluid to position said movable member relative to saidfixed meinber, means operatively connecting said discharge ports withtheir respective fluid pressure responsive neans, means to deliver fluidfrom said source to said first inlet port, means to deliver fluid fromsaid source to said second inlet port, apparatus adapted to bleed fluidfrom said last mentioned means in response to predetermined operatingconditions of said set to thereby regulate the pressure of fluiddelivered to said second inlet port, a fluid pressure responsive valveinterposed in the'path of fluid from said source to said master valveand adapted to prevent the delivery of fluid to said master valve untila predetermined iluid pressure is obtained and means forming a directiluid .flow communication between said source and the fluid pressureresponsive means associated with one of said cylinders and adapted toconcentrate all available fluid pressure thereon until a predeterminedfluid pressure is exceeded and said fluid pressure responsive valve isopened.

6. In a motor driven multi-cylinder compressor set having a first meansfor unloading individual cylinders thereof, a fluid pressure responsivemeans adapted to selectively overrule the action of said first meanswith respect to individual cylinders to load said individual cylindersunder predetermined operating conditions, means to deliver fluid underpressure to said fluid pressure responsive: means including a source offluid under pressure and a master valve adapted tobe positioned by saidfluid, said valve comprising a fixed member and a relatively movablemember, one of said members being provided With' a plurality ofdischarge ports and a first inlet port, said movable inem-ber beingadapted toy control the communication of iluid from said inlet port tosaid individual discharge ports in relation to its position relative tosaid fixed member, said one member having a second inlet port for theadmission of fluid to position said movable member relative to saidiixed member, means operatively connecting said discharge ports withtheir respective iiuid pressure responsive means, means to deliver fluidfrom said source to said first inlet port, means to deliver fluid fromsaidv source to said second inlet port, a first apparatus adapted toreduce the pressure of fluid delivered to said second inlet port whenthe suction pressure in said compressor is less than a predeterminedminimum, a second apparatus adapted to reduce the pressure of fluiddelivered to said second inlet Iport when the suction pressure in saidcompressor exceeds a predetermined maxlmum, and means to deliver all ofthe fluid from said source to the uid pressure responsive meansassociated with at least one of the compressor cylinders and to by-passsaid master valve until a predetermined fluid pressure is exceeded.

7. In a motor driven multi-cylinder compressor set having a rst meansfor unloading individual cylinders thereof, a uid pressure responsivemeans adapted to selectively overrule the action of said first meansWith respect to individual cylinders to load said individual cylindersunder predetermined operating conditions, means to deliver fluid underpressure to said iiuid pressure responsive means including a source vofiiuid under pressure and a master valve adapted to be positioned by saidfluid, Isaid valve comprising a fixed member and la relatively movablemember, one of Isaid members being yprovided with va plurality ofdischarge ports and a first inlet port, said movable member beingadapted to control the communication of fluid from said inlet port tosaid individual discharge ports in relation to its position relative tosaid fixed member, said one member having a second inlet port for theadmission of fluid to position said movable member relative to saidfixed member, means operatively connecting said discharge ports withtheir respective fluid pressure responsive means, mean-s to -deliverfluid from said source to said first inlet port, means to deliver fiuidfrom Isaid source to said second inlet port, said xed member beingprovided with a port so located that under certain conditions it iscovered by said movable member and under other conditions it is exposedto fluid delivered by said last mentioned means and apparatus adapted tocontrol the disposition of fluid entering said klast mentioned port bybleeding increasing amounts of fluid from said fixed member through saidlast mentioned port when the suction pressure in said compressorincreases above a predetermined maximum, the covering ofy said lastmentioned port by said movable member assuring that a predeterminedminimum number of compressor cylinders will be loaded.

8. In a motor driven multi-cylinder compressor set having a first means-for unloading cylinders thereof, a fluid pressure responsive meansadapted to selectively overrule the action of said first means withrespect to individual cylinders under predetermined operatingconditions, means dening a first circuit to deliver fluid under pressureto said fluid pressure responsive means including a source of fluidunder pressure and a master valve adapted to be positioned by said fluidand to `selectively connect said source with the uid pressure responsivemeans of individual cylinders, means defining a second circuit todeliver fluid directly from said source to the fluid pressure responsivemeans of one cylinder and to by-pass said master valve as an incident tostarting of the compressor to thereby concentrate the full pressure ofsaid source on the fluid pressure responsive means of said one cylinderand means to render said second circuit inoperative land said firstcircuit operative after initial starting of the compressor.

ALW'IN B. NEWTON.

References Cited in the le of this patent UNITED STATES PATENTS NumberName Date 1,786,791 Terry Dec. 30, 1930 2,137,219 Aikman Nov. 22, 19382,169,554 Buchanan Aug. 15, 1939 2,185,473 Nees'on Jan. 2, 19402,304,999 Gonzales Dec. 15, 1942 2,387,117 Buehler Oct. 16, 1945

